Fluid apparatus provided with cooperating rotary pistons



Feb. 23, 1932. G. A. UNGAR 1,846,700

FLUID APPARATUS PROVIDED WITH COOPERATING ROTARY PISTONS Filed June 11,1930 5 Sheets-She et l INVENTOR @0577; v5 0N6? ATTORNEYS Feb. 23, 1932.G. A. UNGAR 1,846,700

FLUID APPARATUS PROVIDED WITH COOPERATING ROTARY PISTONS Filed June 11,1930 3 Sheets-Sheet 2' m g. 1o

INVENTOR G'usT/I vs A. UMG/uf ZWQ 5 ATTORNEYS Feb. 23, 1932.

G. A. UNGAR FLUID APPARATUS PROVIDED WITH COOPERATING ROTARY PISTONSFiled June 11, 1930 I5 Sheets-Sheet 3 lN GUSTAV VENTOR a ,4. (/NGAR BY vo 5 ATTORNEYS tion in which cross sections taken plston Patented Feb.23, 1932 G'OSTAVE .A. UNGAR, OF PELEAM MANOR, PATENTS INCORPORATED, OFNEW YORK,

N. Y., A CORPORATION OF NEW YORK FLUID APPARATUS PROVIDED WITHCOOPERA'I'ING ROTARY PISTONS Application filed June 11,

My invention relates to pumps and other apparatus through which a fluidis caused to pass, and more particularly to apparatus of the typeprovided with co-operating rotary pistons. In apparatus of this type asconstructed hitherto, all cross sections of the piston taken in planesperpendicular to the axis of rotation, at different points of such axis,cut the outline or periphery of the piston in profile lines which aresimilar, for each such cross section, bothas to shape and position; or,to express this differently, successive longitudinal or axial sectionsof the piston as constructed hitherto, cut the outline or periphery ofthe piston along lines of the same shape, generally (when theperipheriesof the pistons are cylindrical, in the broad mathematical sense of theterm) straight lines parallel to the axis. With these priorconstructions, rotation of the pistons at a constant angular velocityhas corresponded to considerable irregularities in the rate of the flowof the fluid through the apparatus. Such irregularities will occur withpistons which are cylindrical in the mathematical sense (or straightpistons, as they may be called, since their peripheral surfaces may begenera-ted by' the motion of a straight line), what- .ever profile suchpistons may have. The irregularities or fluctuations will increase withan increase in the ratio betweenthe greatest and the smallest radius ofthe said peripheral surface. The object of my present invention is toremedy this drawback and to obtain a condition i which a practicallyuniform rate of fiow of time fluid will correspond to a constant angularvelocity of the pistons.

For this purpose, I have devised a constructhrough a at successivepoints of its axis of rotation, will vary gradually from one end of thepiston to the other, and in which successive axial sections of thepiston likewise will cut the outline or along varyinglines.

Several satisfactory examples of my invention are shown, as examples, inthe accompanying drawings, in which Fig. 1 shows one form of myinvention in axial section, on line 1-1 of Fig. 2, the latter being adiagramperiphery of the piston 1930. Serial No. 460,309.

matic'cross section, substantially on line 22 of Fig. 1; Fig. 3 is adiagrammatic end view of one of the pistons shown in Fig. 2, and Fig.

NEW YORK, ASSIGNOR 'ro commaoxar.

4 is a corresponding side view, with a representation of the helical orspiral path of a point at which the two pistons come in contact; Figs. 5and 6 are diagrams showing two difierent positions of narrow ordifferential slices of co-operating pistons which have an irregularoutput when rotating at a constant angular speed; Figs. 7, 8 and 8* arediagrammatic views, hereinafter referred to, showing that a uniformoutput is obtained with my invention; Fig. 8 is a section substantiallyon line 8"8 of Fig. 7 Fig. 9 is an axial section, and Fig. 10 is a crosssection illustrating a second embodiment of my invension; Fig. 11 is across section of a third In Figs. 2 and 10, I indicates the inlet and iO the outlet of the casing C having two cylindrical chambers concentricwith the parallel shafts S, S of the rotary pistons P, P, shown as ofsimilar construction, except that one of them is right-hand and theother lefthand, as explained hereinafter. These pis tons are adapted torotate in opposite direc- 1 tions at equal angular velocities, as bymounting on the shafts S, S, spur gears .G, ,G' of. equal diameters.Each piston has end faces of approximately elliptical or oval shape, themajor axis ofthe ellipse or oval bein approximately equal to thediameter 0 chamber in which the piston rotates. The end faces of thesame piston are alike in shape, but differ in them relative position;the major axis of one end being in a position at 9O from the major axisof the other" end, as will be seen best in Fig. 2. The minor radiushalf-axis) of the ellipse or oval is obtaine by subtracting the majorradius the from the distance separating the centers of h the shafts S,S. The piston portion between its ends is of what may be termed of screwformation, that is to say, there. is a gradual twist from one end to theother, and any cross section of the piston (perpendicular to the axis ofrotation) will be of the same oval shape as the ends, but with the axesof the ellipse shifting in position gradually as cross sections aretaken at successive points lengthwise of the axis of rotation. The twistis left-hand for one of the pistons (say the lower piston P), andright-hand for the other. 7

In practice, I prefer that the pistons P, P should not come into actualcontact, but leave a small clearance between the points of closestapproach. This clearance will be constant in all positions of thepistons, and the line of contact, or rather of closest ap proach, will"at all times be continuous from one end face of the pistons to theother; thus there will at no time be any direct communication, orbypass, between the inlet I and the outlet 0, but the fluid has tofollow an arcuate path along the inner walls of the casing chambersduring the rotation of the pistons.

It will be noted from Figs. 2, l0 and 11 that the inlet 1 and the outlet0 are diametrically opposite each other, and these inlet and outletports or connections, may extendpractically the full length of thepistons, as clearly indicated by the dotted rectangles in Figs. 1 and 8The flow of the fluid both to the interior of the casing C and awaytherefrom, will be substantially radial and circumferential, and willnot be axial as it is in certain prior devices.

If the pistons were made of approximately oval cross section, butwithout the longitudinal twist or screw formation described above (thatis, if the pistons were shaped as oval or elliptical cylinders), therate of the flow of the fluid, with a'constant angular velocity of thepistons, would not be uniform but attain a minimum when the major axesof the two ellipses are perpendicular to each other (Fig. 5), and amaximum when they a're parallel'to each other (Fig. 6). These minimaoccur in piston positions 90 apart, while the maxima occur in positionsat &5" from the minima positions. This inequality in the rate of flow'withpistons shaped as elliptical cylinders, increases with theeccentricity of the ellipse, or in other words, with the differencebetween the radii of the ellipse. The une en rate of flow, at aconstantangular velocity of the pistons, will be understood best by aconsideration of the diagrammatic Figs. 5 and 6. Fig. 5 shows thepistons A, B or slices perpendicular to the axis of rotation in aposition in which their major axes are erpendicular to each other, itbeing understood that these pistons or slices have no twist ing theequal I with the area of the sector D, it will be obsuch as thosedescribed with reference to Figs; 1 and 2. If the pistons A, B rotatethrough an'angle 5, the output or delivery of piston A will momentarilybe nil, since the point of contact or of closest approach'of the twopistons is at a circular arc of minimum radius. The output or deliveryof piston B will be a zone sector, within the angle 5, the inner radius1' of said sector being the minimum radius of the piston profile, andthe outer radius R of said zone beingthe maximum radius of said profile.Let us designate the area of said zone sector as D, and this indicatesthe pump output or delivery in the position shown in Fig. 5. When thepistons A, B are in a position in which their major axes are parallel,as in Fig. 6, their rotation through the same angle 5 will produce anoutput or delivery equal to D D each of these two areas D and, D being azone sector, within the angle 9, the inner radius of such sector beingequal to the arithmetical mean,

is equal to the maximum radius R. Compar areas of the sectors D and Dvious, since the sector D narrows uniformly toward its inner end, thatthe outer portions D, D are of larger area than the inner portionsindicated at D In other words, each area D or D is greater than one-halfof the entire sector area D, and consequently, D+D D. Thus, rotation ofthe pistons A, B through the same angle 5 will produce a smaller(minimum) pump delivery D in the vicinity of the position Fig. 5, and agreater (maximum) pump deliveryD'-l-D in the vicinity of the positionFig. 6. In positions intermediate between those shown in Figs. 5 and 6,the output or rate of flow will have a gradually changing intermediatevalue. It will thus be evident'that with straight or cylindrical pistonsor slices (Figs. 5 and 6),

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the rateof flow 'will not be uniform when the pistons are rotated at aconstant angular velocity, but will fluctuate between a maximum and aminimum, which are attained in piston positions 45 apart. Thisfluctuation increases with increase in the ratio The inequalities in therate of fib w, at con" consideration of the diagrammatic Figs. 3.

and 4. Fig. 3 shows the piston P in the same position as Fig. 2, thepoint of contact with, or of closest approach to, the other piston (notshown in this view) being indicated at Y. If we consider a position 90before reaching the one shown in Fig. 4, the point of piston P at whichit was in contact with, or closest to, the other piston, would be theone indicated at X. The points X and Y areat equal distances (R) fromthe center or axis of the piston, but at opposite ends of the piston, aswill be evident from Fi 4. Thus, during the rotation of the pistonthrough an angle of 90?, the shifting point of contact, or of closestapproach, of the two pistons would describe, on the piston P, a helicalline X, Y. In other words, such point of contact or of closest approachwill shift from one end of the piston to the other, during rotationthrough an angle of 90, and back to the first-mentioned end, during therotation through the next 90. The path of the point of contact, or ofclosest approach, on the other piston, would be 'similar to the oneillustrated, except that the helix would run in the opposite direction.Fig. 4 also illustrates the extension of the helical line Y X through Y,X, Y" to the full'360, showing that L, the lead of pitch of the saidhelical line, equals four times the width WV of the piston body.

With the twisted'form of piston explained in connection with Figs. 3 and4, the rate of flow at constant angular speed of rotation 1s no longerfluctuating as in the slices shown in Figs. 5 and 6,.but practicallyuniform, since, as will also appear from Fig. 1, the pistons P, 1?,considered in axial section, have their active surfaces closer to theirrespective axes of rotation at one end of the.

piston than at the other, and this relation is reversed for the twopistons. Thus in Fig. 1 the active surface at the right-hand end ofpiston P is closer to the axis of rotation than the one at the left-handend, while the active surface of piston P is closer to,the axis ofrotation at the left-hand end of the piston than at the right-hand end.a At each moment therefore, the sum or integral of the deliveries madeby all the narrow zones or slices ofthe pistons (slices perpendicular tothe axes of rotation) will be constant, and

therefore the output of the ump will be constant when the pistons P,rotateat a constant angular Velocity. v

Figs. 7, 8 and 8 further illustrate these conditions, Fig. 7 showing thepistons P, P

in a position in which their major axes are parallel (45 from theposition shown in Fig. 2). Within the angles or, the piston outline (inend view or cross section) is a circular arc, and the correspondinghelical bands 0, c are portions of circular cylinders, the inner bands 0being portions of a circular cylinder with the radius 1', While theouter bands 0 are portions of a circular cylinder with the radius R. Theprovision of cylindrical surface portions as at 0 and c, is of advantagein that it enables me to preserve at all times, adjacent to the inlet Iand the I outlet 0, a suflicient amount of overlap Lto insure aneflicient seal at these points and to j prevent any short-circuiting ordirect flow from the inlet I to' the outlet 0. The inter-' mediateportions 0" of the outer or active piston surfaces are twisted, ornon-cylindrical. The diagram Fig. 8 shows a development of the pistoncircumference, and (at the right) a developed profile of the rotor orpiston. Fig.- 8 is a diagram illustrating the fluid'delivery of the twopistons in the longitudinal plane indicated atww in Fig. 8.

While within such plane the delivery, or rate through the axes of bothpistons when the major axes of their corresponding elliptical end facesare perpendicular to each other,

will show the line of contact, or-of closest approach, as a reversecurve one end of which is nearer to the axis of one piston than theother end. If transverse sections were taken in positions of the pistonsintermediate between those just referred to, they would show a gradualtransition in the longitudinal shape of the line of contact, or ofclosest approach.

Asa variant of the one-piece pistons the outlines of which ,have acontinuous twist or screw-shape from one end to the other, I havedevised a construction of such pistons in cylindrical laminations .orslices alike in shape, but secured together to form an approximation tothe screw-shape shown in Figs. 1 to 4. Such approximation can beincreased by using a greater number of slices, of correspondinglyreduced thick ness. Figs. 9 and 10 illustrate this con- 'struction ofbuilt-up pistons. Each of the slices p or p is of the same shape, viz.that of a thin plate or slice of the form of an approximatey ellipticalor oval cylinder, and can be manufactured readily by stamping sheetmetal, or other inexpensive methods. The individual plates'orlaminations of the same pistons are of equal thickness, and would be setin positions shifted or displaced angularly to each othen, by equalamounts, in such a manner that the angular shifting of thelastlamination relatively to the first will amount to 90, in theparticular case illustrated. The laminations may be held in the properposition in any suitable manner, for instance by means of a key passingthrough properly positioned keyways in the iii successive laminations.If there are n laminations, the angular lead of each over its neighborwill be in the particular case referred to; for instance; with ninelaminations, the angular lead, from one lamination to the next, will be10. It is true that, considering each lamination alone, the pistonoutline, within that lamination, will have the shape of anellipticalcylinder; yet the succession of these short ellipticalcylinders, in somewhat step-like arrangement, as shown, will form aclose approximation to the exact theoretical twisted or screw-surfacedescribed in connection with the first form of my invention. Inpractice, especially with a large number of laminations, this built-upconstruction of pistons will yield avirtually uniform rate of flow ofthe fluid, with a constant angular velocity of the pistons.

My invention is not restricted to pistons of elliptical or oval outline,but various other shapes may be employed. The piston outline, however,should always be symmetrical to the axis of rotation, and selected so asto provide rolling of the profile of one piston on the other, or with aconstant clearance (1. c. without actual contact) when the two pistonsare rotating in opposite directions with equal angular velocities. Anexample of such other shapes is shown in Fig. 11, where the piston hasascrew-shape, with a lead of 90 from one end to the other, as in Figs, 1to 4 and 7 to 10, but the piston outline includes circular arcs a anda,v (for instance of 30) centered upon the axes of the respectivepistons, and suitable connecting portions 6. With outlines formed partlyof circular arcs, I am enabled to use circumferentially wider inlet andoutlet openings at I and 0 respectively, but otherwise this form of myinvention has the same advantages as the constructions described above.

Still another form of my invention is shown in Figs. 12 to 17-. Herecross sections taken through the same piston at different points. along.its axis of rotation are not of like outline, as in the constructionsdescribed above, but such outline varies lengthwise of said axis. Yet,in this form also, I use a screw formation or longitudinal twist oncertain portions of the co-operating piston outlines. Each piston 19 phas cylindrical por tions 1), 19* respectively of circular cross sectionand of the same diameter, the axes of these portons coinciding with theaxes of the respective pistons. Each pistdn 22 p furthermore hascylindrical portions p, p respectively, likewise of circular crosssection,

but of a diameter smaller than that of the portions 12 ,17 and co-axialtherewith. The portions p p and p, p are connected by ,corresponding tothe aeaaaoo helical surfaces 12 10 respectively constitutportions 17 prespectively. The helical portions 20 p are of uniform pitch from oneend face of each piston to the other, and the lead is 90 from one end tothe other, as in the forms described above. On one piston, the outer orrelatively raised portions p are of diamond shape in developed view(Fig. 13) and the inner or relatively depressed portions 39 aretriangular, with their-bases at the ends of the piston, and their apicesat its median transverse plane. On the other piston, the arrangement isreversed,.the triangular raised portions 2 matching the depressedtriangular portions 19 of theother cylinder, while the diamond-shapeddepressed portions 2 match the like raised portions 19*. It will beevident that the outline of each piston, in successive cross sectionstaken along its axis of rotaton, will vary gradually from one end of thepiston to the other. The formation of the helical surfaces 39 ,7) issuch that during the rotation of the two pistons their. points ofcontact, or of closest approach, will at all times form a continuousline from one endof the piston to the other.

Fig. 13 is a developed view, being virtually a section taken in thecylindrical surfaces (pitch surfaces) indicated in Figs. 10, 11 and 12by the dotted circles between those inner surfaces 29 p and to the outersurfaces 10 p respectively. The left half ofFig. 13 shows the piston parid the right half shows the piston 79 It will'be obvious that at anyparticular moof. three quantities: First, the quantity Q. at.

such points where the outer portion 29 of the piston p cooperates withthe inner portion p of the other piston 22 second, the quantity Q atsuch points where the inner portion p of the piston 19 co-operates withi the outer portion 19 of the other piston 77; and third, the quantityQ,at those points where the helical portions of the two pistonsco-operate. If we consider the slightly changed condition obtainingafter the pistons have rotated through an angle (,0, the relativecontributions to the quantities Q, and Q (Q being constant) will. havevaried, but the total amount Q Q+Q +Q, remains the same, thus showingthat a uniform rate of flow corresponds to a constant angular velocityof the pistons.

The construction illustrated by Figs. 12 to 17 is what may be termed adevice provided with rotary pistons each having two teeth of a crosssection varying lengthwise of the axis. This form of my invention mightbe carried out in other ways, as long as the sum of the individual flowquantities Q, Q Q, remains constant, which will be the case when theflanks of the teeth form helical surfaces of constant pitch;

I desire it to be understood, however, that my invention is not limitedto a construction in which the pistons are each provided with twoportions of large diameter and two portions of small diameter, or, inother words, with two teeth; the invention is applicable toconstructions in which the piston has more than two teeth or points, orportions of large diameter, and particularly to the form of pumps knownas gear pumps, whose pistons resemble gear wheels.

In practice, the shaft of one of the co-operating pistons (in anyembodiment of my invention) is extended so that power may be applied tothe device when it is used as a pump or for similar purposes, or thatpower may be taken from the device if it is driven by the flow of fluid.

The toothed form exemplified by Figs. 12 I to 16 gears one piston to theother and enables me to dispense with gears such as shown at G G in Fig.1; yet even in connection with this toothed form, I consider theemployment of gears (corresponding to G, G) desirable,

in order to prevent wear of the co-operating pistons.

I claim:

1. A fluid apparatus comprising a casing having an inlet and an outletdiametrically opposite to said inlet, and cooperating pistons mounted insaid casing to rotate about axes located in a plane substantiallyperpendicular to the line joining the inlet and the outlet, said pistonshaving helical portions of substantially uniform pitch extending axial-1y thereof, said inlet and outlet being substantially as wide as theaxial length of said pistons, whereby a constant volume flow isobtained.

2. A fluid apparatus according to claim 1, in which the helical pistonportions have a lead of from one end of a piston to the other. I

3. A fluid apparatus according to claim 1,

in which the plston is built up of laminations,

transverse to the axis of notation, said laminations being ofsubstantially elliptical outline of like shape, but with their axesshifted by. equal angles from one lamination to the a next, to produce ahelical surface.

my hand,

4. A fluid apparatus accordin to claim 1, in which the cross section ofeac piston has an outline composed of circular arcs of two di erentradii and connecting portions between arcs of difi'erent radii.

In testimony swhereoef I have hereunto set GUSTAVE A. UNGAR.

